A multitude of liquid filters is previously known for filtering liquids used for various purposes. For example, when filtering lubricating oil for internal combustion engines, the oil is circulated between an oil reservoir and the lubrication points, the oil being brought to pass through an oil filter during the circulation. The filter is typically located in a so-called shunt or by-pass line so as to clean a fraction of the oil during each circulation passage. However, up to now, only a limited cleaning degree has been achieved, causing the oil to successively age and deteriorate with regard to its properties. Thus, up to now, you have been required to exchange the oil after a certain limited time.
Taking care of used oil is a very substantial environmental problem, not least if regarded worldwide, and therefore an improved degree of cleaning would result in large gains with regard to environment as well as economy. By extending the service life of certain types of liquids, such as oils, to a large extent being extracted from nature, the natural resources of the earth would be extended substantially.